The shipment of relatively small quantities of refrigerated or cooled materials is frequently required in the course of medical and scientific research. The quantity of material which must be shipped may be of such small size that delivery by express or courier service is feasible and cost effective so long as the material remains chilled. Conventional shipping containers do not, unfortunately, provide adequate thermal insulation for maintaining the materials cooled. Furthermore, the quantity of material being shipped is so slight that conventional refrigerated shipping units are unfeasible.
Medical and scientific research may require that material which is sensitive to temperature fluctuations be transmitted between two distant locations. This is a typical situation in such diverse areas as organ transplants and biotechnology. Shipment of these materials requires that they be maintained at a chilled temperature throughout the shipping period or else suffer the possibility of severe degradation.
The materials being shipped must also be protected from violent impacts and rough handling. Consequently, the container in which the material is shipped must have substantial structural integrity. Additionally, the container in which the material is shipped must be capable of withstanding point impacts of substantial force.
Ernst, et al, U.S. Pat. No. 3,890,762, discloses a produce shipping container and packing method. That patent discloses the use of a carton liner which is manufactured from polystyrene foam having a particular density. The foam is cut into portions which provide the top, bottom and sides for the liner. The sides have straight edges which bear one against the other.
Tatsch, U.S. Pat. No. 3,251,382, discloses a foldable conduit structure comprised of a plurality of interconnected rigid plastic foam panels. At least some of the panels have beveled edges to permit the panels to be folded into a rectangular configuration. The foam panels have a non-perforated metal structural skin bonded to one side thereof.
Brock, U.S. Pat. No. 3,420,022, discloses a concrete insulation blanket. A portable blanket has a water impervious elongated plastic film cover. The plastic film cover surrounds at least one sheet of flexible material.
None of these patents, either alone or in combination, solves the problem of providing a reusable insulated box permitting refrigerated materials to be shipped long distances, without the need of external refrigeration, while maintaining the materials chilled. None of the patents discloses a reusable insulated box which is capable of withstanding rough handling by the shipper. None of the patents discloses an insulated box which includes integral means for maintaining dimensional and structural stability of the box. Finally, none of those patents disclose the utilization of heat shrinkable materials for sheathing the insulation plates of which the box is manufactured in order to greatly improve the resistance to temperature changes. The use of heat shrinkable polyvinyl chloride film not only improves the temperature resistance of the box components but also permits the components to be cleaned after use.